swc-windows-installer.py: Extract nano directly to the install directory
swc-windows-installer.py: Extract nano directly to the install directory

This is more efficient than "extract to . and then copy".  I also
renamed the install_nano() argument.  The function doesn't care that
we're currently passing the Python script directory; it will work
perfectly well with a different directory in the PATH.

selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,ethanwhite/windows-installer,selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,swcarpentry/windows-installer,wking/swc-windows-installer,selimnairb/2014-02-25-swctest